The invention relates to a method for controlling robots for welding three-dimensional workpieces.
In shipbuilding, micropanels are used which comprise steel plates and reinforcing profiles welded thereon. In the initial situation, these reinforcing profiles of different types are tack-welded onto the steel plates and subsequently welded by bent arm robots or portal welding units. The profiles are distinguished by different profile shapes, dimensions and end cut edges, the arrangement of the profiles on the plates is possible in any way. However particularly in the case of small piece numbers as is the case with micropanels in shipbuilding, the movement programming of the welding robots for the track welding represents a disproportionately high complexity in the entire, otherwise automated manufacturing process.
At present, almost all programming methods for the welding of three-dimensional workpieces in shipbuilding are based on the availability and subsequent conversion of the respective CAD data. In addition to interface problems and the problems of compatibility of different CAD programmes and their output data files for the normally used CAM module, these programming methods are associated with a highly restricted possibility of reacting to temporarily changing constructional or technological features of the component to be welded. If a panel changes temporarily in that profiles are missing, have constructional additions or the arrangement thereof is changed, nevertheless the original, no longer relevant robot programme is run. A further problem in the previous modus operandi is the necessity for orientation of the workpiece according to the robot programme or the displacement and reorientation of the programme corresponding to the position of the component.
In the state of the art, a further method for controlling and programming welding robots is known (EP 1 188 510 A2), in which a two-dimensional photo of the constructional template with the workpieces distributed thereon is produced by means of a camera. From the image data, the programme recognises profile lines in plan view by means of contrast differences. The limitation of this method resides in the fact that neither the profile heights, i.e. the length of vertical seams, nor cutouts and different start and end cut edges of the profiles can be recognised. In addition, in order to initiate the programme, relatively comprehensive interactive inputs from the operator are required, which describe in particular the starting and end conditions of the weld seams.